fix: use pre-defined relays for autorelay

Unfortunately, we don't currently have any way to pick out good relays from bad.
That means we keep searching, trying bad relays, searching some more, trying
_the same relays_, etc. until we randomly find 3 good stable relays. In
practice, this means we just keep searching forever and keep thrashing the DHT.

see libp2p/go-libp2p#694

core/node/libp2p/relay.go

@@ -11,7 +11,7 @@ func Relay(disable, enableHop bool) func() (opts Libp2pOpts, err error) {
 			// Enabled by default.
 			opts.Opts = append(opts.Opts, libp2p.DisableRelay())
 		} else {
-			relayOpts := []relay.RelayOpt{}
+			relayOpts := []relay.RelayOpt{relay.OptDiscovery}
 			if enableHop {
 				relayOpts = append(relayOpts, relay.OptHop)
 			}
@@ -21,4 +21,4 @@ func Relay(disable, enableHop bool) func() (opts Libp2pOpts, err error) {
 	}
 }
 
-var AutoRelay = simpleOpt(libp2p.ChainOptions(libp2p.EnableAutoRelay(), libp2p.DefaultStaticRelays()))
+var AutoRealy = simpleOpt(libp2p.ChainOptions(libp2p.EnableAutoRelay(), libp2p.DefaultStaticRelays()))